List, I've completed the second paper in my series analyzing Sophos
Antivirus internals, titled "Practical Attacks against Sophos
Antivirus". As the name suggests, this paper describes realistic
attacks against networks using Sophos products.
The paper includes a working pre-authentication remote root exploit
that requires zero-interation, and could be wormed within the next few
days. I would suggest administrators deploying Sophos products study
my results urgently, and implement the recommendations.
I've also included a section on best practices for Sophos users,
intended to help administrators of high-value networks minimise the
potential damage to their assets caused by Sophos.
The paper is available to download at the link below.
https://lock.cmpxchg8b.com/sophailv2.pdf
A working exploit for Sophos 8.0.6 on Mac is available, however the
techniques used in the exploit easily transfer to Windows and Linux,
due to multiple critical implementation flaws described in the paper.
Testcases for the other flaws described in the paper are available on
request.
https://lock.cmpxchg8b.com/sophail-rev3-exploit.tar.gz
It is my understanding that Sophos plan to publish their own advice to
their customers today. I have not been given an opportunity to review
the advice in advance, so cannot comment on it's accuracy.
I have had a working exploit since September, but Sophos requested I
give them two months to prepare for this publication before discussing
it. A timeline of our interactions is included in the paper. I believe
CERT are also preparing an advisory. I'm currently working on the
third paper in the series, which I'll announce at a later date. Please
contact me if you would like to be a reviewer. I will add any last
minute updates to twitter, at http://twitter.com/taviso.
If you would like to learn more about Sophos internals, you can read
my previous paper in the series here
https://lock.cmpxchg8b.com/sophail.pdf
I've reproduced a section of the conclusion below.
Tavis.
Conclusion
As demonstrated in this paper, installing Sophos Antivirus exposes
machines to considerable risk. If Sophos do not urgently improve their
security posture, their continued deployment causes significant risk
to global networks and infrastructure.
In response to early access to this report, Sophos did allocate some
resources to resolve the issues discussed, however they were cearly
ill-equipped to handle the output of one co-operative, non-adversarial
security researcher. A sophisticated state-sponsored or highly
motivated attacker could devastate the entire Sophos user base with
ease.
Sophos claim their products are deployed throughout healthcare,
government, finance and even the military. The chaos a motivated
attacker could cause to these systems is a realistic global threat.
For this reason, Sophos products should only ever be considered for
low-value non-critical systems and never deployed on networks or
environments where a complete compromise by adversaries would be
inconvenient.
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